NAV setting method considering BSS color inactivation in wireless LAN system and apparatus therefor

ABSTRACT

When an AP detects a collision between a neighbor BSS and a BSS color in a wireless LAN system, the AP can inform an STA of the same through information indicating whether the BSS color is disabled, and set and transmit a TXOP_duration field of a transmitted frame to a specific value differentiated from a normal duration value in order to prevent an erroneous NAV setting of the STA.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 15/774,259,filed on May 7, 2018, currently pending, which is the National Stagefiling under 35 U.S.C. 371 of International Application No.PCT/KR2017/004404, filed on Apr. 26, 2017, which claims the benefit ofU.S. Provisional Application No. 62/327,445, filed on Apr. 26, 2016,62/412,226, filed on Oct. 24, 2016, 62/434,423, filed on Dec. 15, 2016,and 62/433,795, filed on Dec. 14, 2016, the contents of which are allhereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present specification relates to a wireless LAN system, and moreparticularly, to a method of setting a NAV in consideration ofdisablement of a BSS color in a wireless LAN system and an apparatustherefor.

BACKGROUND ART

A method described in the following can be applied to various wirelesscommunications. In the following, a WLAN (wireless local area network)system is explained as an example of a system to which the presentinvention is applicable.

Standards for a Wireless Local Area Network (WLAN) technology have beendeveloped as Institute of Electrical and Electronics Engineers (IEEE)802.11 standards. IEEE 802.11a and b use an unlicensed band at 2.4 GHzor 5 GHz. IEEE 802.11b provides a transmission rate of 11 Mbps and IEEE802.11a provides a transmission rate of 54 Mbps. IEEE 802.11g provides atransmission rate of 54 Mbps by applying Orthogonal Frequency DivisionMultiplexing (OFDM) at 2.4 GHz. IEEE 802.11n provides a transmissionrate of 300 Mbps for four spatial streams by applying Multiple InputMultiple Output (MIMO)-OFDM. IEEE 802.11n supports a channel bandwidthof up to 40 MHz and, in this case, provides a transmission rate of 600Mbps.

The above-described WLAN standards have evolved into IEEE 802.11ac thatuses a bandwidth of up to 160 MHz and supports a transmission rate of upto 1 Gbits/s for 8 spatial streams and IEEE 802.11ax standards are underdiscussion.

DISCLOSURE OF THE INVENTION Technical Tasks

In IEEE 802.11ax system, discussion on an intra-PPDU power saving methodis in progress. According to the intra-PPDU power saving method, if anSTA (station) receives a frame not received by the STA in a BSS to whichthe STA belongs, the STA enters a doze state until the frame ends toprevent power consumption of the STA.

In this case, BSS color information, which is used for the STA toidentify whether or not a received frame corresponds to a frame of theSTA, is represented by the limited number of bits. As a result, acollision occurs between a neighbor BSS and BSS color and an error mayoccur.

When a collision occurs in the aforementioned BSS color, an object ofthe present invention is to provide a method of efficiently inducing anSTA to reduce power consumption and an apparatus therefor.

The present invention is not restricted to the aforementioned technicaltask and other technical tasks can be derived from embodiments of thepresent invention.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of controlling a NAV (network allocationvector) setting of an STA (station), which is controlled by an AP(access point) in a wireless LAN system, includes the steps of detectinga BSS (basic service set) color overlap with an OBSS (overlapping basicservice set), transmitting a first frame including BSS color disabledinformation set to a first value indicating disablement of BSS colorinformation to the STA, and transmitting a second frame including aTXOP_DURATION field set to a specific value differentiated from a normalduration value to the STA.

If a value of the TXOP_DURATION field is set to the specific value, theSTA may not update a NAV based on the value of the TXOP_DURATION field.

Although BSS color of the second frame is identical to BSS color of aBSS to which the STA belongs thereto, the BSS color disabled informationset to the first value can make the STA update an inter-BSS NAV.

If a value of the TXOP_DURATION field is set to the specific value, theSTA may not update the inter-BSS NAV.

If a value of the TXOP_DURATION field is set to the specific value, theSTA may operate based on an EIFS (extended inter-frame space).

A specific value of a value of the TXOP_DURATION field may correspond toa value that all bits are set to 1.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, amethod of configuring a NAV (network allocation vector) of an STA(station) in a wireless LAN system includes the steps of receiving afirst frame including BSS color disabled information set to a firstvalue indicating disablement of BSS (basic service set) colorinformation from an AP (access point), and receiving a second frameincluding a TXOP_DURATION field set to a specific value differentiatedfrom a normal duration value from the AP. In this case, if a value ofthe TXOP_DURATION field is set to the specific value, the STA may notupdate a NAV based on the value of the TXOP_DURATION field.

The first frame including the BSS color disabled information set to thefirst value can be received when the AP detects a BSS (basic serviceset) color overlap with an OBSS (overlapping basic service set).

If the BSS color disabled information set to the first value isreceived, the STA can update an inter-BSS NAV, although BSS color of thesecond frame is identical to BSS color of a BSS to which the STA belongsthereto.

If a value of the TXOP_DURATION field is set to the specific value, theSTA may not update the inter-BSS NAV.

If a value of the TXOP_DURATION field is set to the specific value, theSTA may operate based on an EIFS (extended inter-frame space).

A specific value of a value of the TXOP_DURATION field may correspond toa value that all bits are set to 1.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, an AP controlling a NAV (network allocation vector) settingof an STA (station) in a wireless LAN system includes a processorconfigured to detect a BSS (basic service set) color overlap with anOBSS (overlapping basic service set), and if the processor detects a BSScolor overlap, a transceiver configured to transmit a first frameincluding BSS color disabled information set to a first value indicatingdisablement of BSS color information, and a second frame including aTXOP_DURATION field set to a specific value differentiated from a normalduration value to the STA under the control of the processor.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, an STA (station) performing a NAV (network allocationvector) setting in a wireless LAN system includes a transceiverconfigured to receive a first frame including BSS color disabledinformation set to a first value indicating disablement of BSS (basicservice set) color information, and a second frame including aTXOP_DURATION field set to a specific value differentiated from a normalduration value from the AP, and if a value of the TXOP_DURATION field isset to the specific value, a processor configured not to update a NAVbased on the value of the TXOP_DURATION field.

Advantageous Effects

According to the aforementioned scheme, although a collision occurs inBSS color, it is able to efficiently induce an STA to reduce powerconsumption.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an exemplary configuration of a WLANsystem;

FIG. 2 is a diagram illustrating another exemplary configuration of aWLAN system;

FIG. 3 is a diagram for an exemplary configuration of a WLAN system;

FIG. 4 illustrates an awake state and a sleep state defined in 11ax;

FIG. 5 is a diagram for explaining an intra-PPDU power saving schemeaccording to one embodiment of the present invention;

FIG. 6 is a diagram for explaining a format of a HE operation parametersfield according to one embodiment of the present invention;

FIG. 7 is a flowchart for explaining an intra-BSS power saving scheme ofan STA according to one embodiment of the present invention;

FIG. 8 is a diagram illustrating a scheme of informing an STA of BSScolor disabled via a beacon according to one embodiment of the presentinvention;

FIG. 9 is a diagram illustrating a scheme of informing an STA of BSScolor disabled via a response message in response to a request of an STAaccording to one embodiment of the present invention;

FIG. 10 is a diagram illustrating a scheme of informing an STA of BSScolor disabled irrespective of a request of an STA according to oneembodiment of the present invention;

FIG. 11 is a diagram for explaining a scheme of controlling a NAVsetting according to one embodiment of the present invention;

FIG. 12 is a diagram for explaining a scheme of updating a NAV when TXOPduration has a normal value according to one embodiment of the presentinvention;

FIG. 13 is a diagram for explaining a scheme of updating a NAV when TXOPduration is set to all is according to one embodiment of the presentinvention;

FIG. 14 is a block diagram illustrating an exemplary configuration of anAP (or, a base station) and a station (or, a user equipment) accordingto one embodiment of the present invention;

FIG. 15 illustrates an exemplary configuration of a processor of an APor a station according to one embodiment of the present invention.

BEST MODE Mode for Invention

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the present invention.The following detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details.

FIG. 1 is a diagram illustrating an exemplary configuration of a WLANsystem.

As illustrated in FIG. 1, the WLAN system includes at least one BasicService Set (BSS). The BSS is a set of STAs that are able to communicatewith each other by successfully performing synchronization.

An STA is a logical entity including a physical layer interface betweena Media Access Control (MAC) layer and a wireless medium. The STA mayinclude an AP and a non-AP STA. Among STAs, a portable terminalmanipulated by a user is the non-AP STA. If a terminal is simply calledan STA, the STA refers to the non-AP STA. The non-AP STA may also bereferred to as a terminal, a Wireless Transmit/Receive Unit (WTRU), aUser Equipment (UE), a Mobile Station (MS), a mobile terminal, or amobile subscriber unit.

The AP is an entity that provides access to a Distribution System (DS)to an associated STA through a wireless medium. The AP may also bereferred to as a centralized controller, a Base Station (BS), a Node-B,a Base Transceiver System (BTS), or a site controller.

The BSS may be divided into an infrastructure BSS and an Independent BSS(IBSS).

The BSS illustrated in FIG. 1 is the IBSS. The IBSS refers to a BSS thatdoes not include an AP. Since the IBSS does not include the AP, the IBSSis not allowed to access to the DS and thus forms a self-containednetwork.

FIG. 2 is a diagram illustrating another exemplary configuration of aWLAN system.

BSSs illustrated in FIG. 2 are infrastructure BSSs. Each infrastructureBSS includes one or more STAs and one or more APs. In the infrastructureBSS, communication between non-AP STAs is basically conducted via an AP.However, if a direct link is established between the non-AP STAs, directcommunication between the non-AP STAs may be performed.

As illustrated in FIG. 2, the multiple infrastructure BSSs may beinterconnected via a DS. The BSSs interconnected via the DS are calledan Extended Service Set (ESS). STAs included in the ESS may communicatewith each other and a non-AP STA within the same ESS may move from oneBSS to another BSS while seamlessly performing communication.

The DS is a mechanism that connects a plurality of APs to one another.The DS is not necessarily a network. As long as it provides adistribution service, the DS is not limited to any specific form. Forexample, the DS may be a wireless network such as a mesh network or maybe a physical structure that connects APs to one another.

FIG. 3 is a diagram for an exemplary configuration of a WLAN system.FIG. 3 shows an example of a base structure BSS including a DS.

According to an example shown in FIG. 3, a BSS1 and a BSS 2 construct anESS. In a WLAN system, an STA corresponds to a device operatingaccording to MAC/PHY regulation of IEEE 802.11. An STA includes an APSTA and a non-AP STA. In general, the non-AP STA corresponds to such adevice directly handled by a user as a laptop computer, a mobile phoneand the like. In the example of FIG. 3, an STA 1, an STA 3 and an STA 4correspond to the non-AP STA and an STA 2 and an STA 5 correspond to theAP STA.

In the following description, the non-AP STA may be referred to as aterminal, a WTRU (wireless transmit/receive unit), a UE (userequipment), an MS (mobile station), a mobile terminal, an MSS (mobilesubscriber station) and the like. And, an AP is a concept correspondingto a BS (base station), a Node-B, an eNB (evolved Node-B), a BTS (basetransceiver system), a femto BS, and the like in a different wirelesscommunication field.

As mentioned in the foregoing description, the present invention relatesto a power saving mode of an STA in a next generation WLAN system(802.11ax). In particular, the present invention relates to operationsof UEs that an HE-STA operates as an intra-PPDU PS for HE PPDU (HE UL SUPPDU, HE MU PPDU, HE trigger-based PPDU) including BSS color.

To this end, first of all, a power saving scheme in 11ax is explained.

FIG. 4 illustrates an awake state and a sleep state defined in 11ax.

In general, a sleep state (or, a doze state) can include a shallow sleepstate and a deep sleep state. The deep sleep state corresponds to asleep state consuming minimum power (non-zero) and requires longest timeto switch to a listen state. The shallow sleep state corresponds to asleep state consuming power relatively greater than power consumed bythe deep sleep state. The shallow sleep state can more quickly switch tothe listen state compared to the deep sleep state.

Meanwhile, definition on the shallow sleep state and the deep sleepstate can be modified as follows. The deep sleep state corresponds to astate that a wireless communication (wireless radio) is turned off, i.e.a sleep state that RF, a baseband processor, and a MAC processor are allswitched off. In the deep sleep state, leakage power can be consumedonly. The shallow sleep state may correspond to a state that RF isswitched off while a baseband processor and a MAC processor are turnedon.

Table 1 shows an example of current consumption in the deep sleep state.

TABLE 1 Power State parameters Average Current Consumption [mA] Voltage= 1.1 V, Band = {2.4 GHz, 5 GHz}, NSS = {1}, Number of TX/RX antennas ={1}, TX power per antenna = {15 dBm} Bandwidth = Bandwidth = Bandwidth =Power State {20 MHz} {40 MHz} {80 MHz} Transmit 280 mA 280 mA 280 mAReceive 100 mA 140 mA 200 mA Listen 50 mA 60 mA 75 mA Shallow Sleep 0.9mA 0.9 mA 0.9 mA Deep Sleep 0.09 mA 0.09 mA 0.09 mA

Table 2 shows power and latency of state transition of 802.11ax.

TABLE 2 Power Transition parameters Average Power State TransitionsTransition Time (ms) Consumption (mW) Transmit to Listen T_(TL) = 0.01ms 75 mW Receive ⇔ Listen 0.001 ms 55 mW Listen to Transmit T_(LT) =0.01 ms P_(LT) = 100 mW Transmit to Shallow T_(TS) = 0.01 ms P_(TS) = 15mW Sleep Receive to Shallow T_(RS) = 0.2 ms PRS = 15 mW Sleep Listen toShallow T_(LS) = 0.2 PLS = 5 mW Sleep Shallow Sleep to 0.5 ms (T_(SL))Listen Listen to Deep T_(LD) = 1 ms P_(DS) = 5 mW Sleep Deep Sleep toT_(SDL) = 10 ms Listen

If an STA supporting HE PPDU (hereinafter, HE STA) receives intra-BSSPPDU (e.g., non-HT, VHT, or HE PPDU) and the received intra-BSS PPDU isnot intended for the HE STA, the HE STA can reduce power consumption byswitching to a doze state.

Intra PPDU PS Operation for HE PPDU

If an STA supporting HE PPDU (hereinafter, HE STA) receives intra-BSS HEPPDU and the received intra-BSS PPDU is not intended for the HE STA, theHE STA can reduce power consumption by switching to a doze state. Inthis case, in order to determine whether or not the HE PPDU correspondsto intra-BSS PPDU, the HE STA may use BSS color information included inHE-SIG A.

FIG. 5 is a flowchart for explaining an intra-PPDU power saving schemeaccording to one embodiment of the present invention.

As shown in FIG. 5, if an STA receives a specific frame (hereinafter,‘first frame’) [S510], the STA can determine whether or not BSS color ofthe received first frame is matched with BSS color of a BSS associatedwith the STA [S520]. If the BSS color of the received first frame is notmatched with the BSS color of the STA, the STA maintains an awake state[S550]. If the BSS color of the first frame is matched with the BSScolor of the STA and the first frame is not a frame transmitted to theSTA [S530], the STA can enter a doze state until the first frame ends[S540].

Specifically, (i) a case that an HE STA receives HE DL MU PPDU (ILFLAG=0) is explained. If BSS color information of a PPDU is matched withcolor information of a BSS associated with the HE STA and an identifieror a broadcast/multicast identifier of the STA is not included in HE-SIGB, the HE STA can enter a doze state until the HE DL MU PPDU ends. (ii)A case that the HE STA receives HE UL MU PPDU (UL FLAG=1) is explained.If BSS color information of a PPDU is matched with color information ofa BSS associated with the HE STA, the HE STA can enter a doze stateuntil the HE UL MU PPDU ends. (iii) A case that the HE STA receives HESU PPDU is explained. If BSS color information of a PPDU is matched withcolor information of a BSS associated with the HE STA and a UL/DLindicator indicates UL, the HE STA can enter a doze state until the HESU PPDU ends.

Collision Problem of BSS Color

As mentioned in the foregoing description, according to 11ax intra-PPDUpower saving operation, if BSS color is matched with BSS color of an APassociated with HE STA based on BSS color included in HE-SIG A, the HESTA can reduce power consumption by entering a doze state until theremaining part of PPDU duration. However, if BSS color is used by adifferent BSS, the HE STA may enter the doze state after HE PPDU of OBSSis received. Hence, the HE STA may fail to receive PPDU of the HE STA.

According to the current discussion, the BSS color information includedin the HE-SIG A has a size of 6 bits. Hence, confusion may occur with asurrounding BSS. In order to solve the confusion, it may consider ascheme of increasing the size of the BSS color. However, the scheme ofincreasing the size of the BSS color may cause an unnecessary signalingoverhead problem.

And, as mentioned in the foregoing description, when a collision occursbetween BSS colors, it may consider a scheme of indicating whether toperform power saving whenever PPDU is transmitted to prevent that an STAperforms a wrong intra-PPDU power saving operation. However, the schememay also cause unnecessary signaling overhead.

Therefore, as mentioned in the foregoing description, if an AP detects acollision of BSS color, a preferred embodiment of the present inventionproposes a method that the AP informs an STA of information fordisabling a BSS color-based operation.

Scheme of Indicating Disable of BSS Color-Based Operation

According to the present embodiment, an AP can activate or inactivate(disable) an intra-PPDU power saving operation operating based on BSScolor of STAs. If a collision of BSS color is detected (i.e., if it isdetermined that a different BSS uses the same BSS color), the AP candisable BSS color-based intra-PPDU power saving of the STAs.

FIG. 6 is a diagram for explaining a format of a HE operation parametersfield according to one embodiment of the present invention.

HE STAs belonging to a HE BSS can be controlled by HT operation element,VHT operation element, and HE operation element. Among the elements, theHE operation element related to a HE operation is shown in FIG. 6.

Referring to FIG. 6, a BSS color field may indicate BSS colorcorresponding to an AP, an IBSS STA, a mesh STA, or a TDLS STA, whichhas transmitted a corresponding element. In the present embodiment,assume that the BSS color maintains a size of 6 bits.

Meanwhile, as shown in FIG. 6, the HE operation element can additionallyinclude a BSS color disabled subfield. In the present embodiment, if anAP recognizes overlap of BSS color with a neighboring BSS, the AP candisable a BSS color based operation by configuring the BSS colordisabled subfield by 1. Besides, the BSS color disabled subfield can beset to 0.

FIG. 7 is a flowchart for explaining an intra-BSS power saving scheme ofan STA according to one embodiment of the present invention.

As shown in FIG. 7, if an STA receives a first frame [S710], the STA candetermine whether a BSS color disabled field value of a most recentlyreceived HE operation element corresponds to 1 or 0 [S720]. Thereception of the HE operation element is explained in detail in thefollowing.

If the value of the BSS color disabled field is set to 1 to indicate thedisable of the BSS color based operation, the STA can maintain an awakestate without performing an intra-PPDU power saving operation [S760]. Ifthe BSS color disabled field indicates 0, as mentioned earlier withreference to FIG. 5, the STA compares BSS color of the received firstframe with BSS color of the STA [S730], determines whether or not thereceived first frame corresponds to a frame transmitted to the STA[S740], and may be then able to determine whether to enter a doze stateaccording to intra-PPDU power saving [S750].

Specifically, (i) a case that an HE STA receives HE DL MU PPDU (ILFLAG=0) is explained. If BSS color information of a PPDU is matched withcolor information of a BSS associated with the HE STA, an identifier ora broadcast/multicast identifier of the STA is not included in HE-SIG B,and a value of a BSS color disabled field of a most recently received HEoperation element corresponds to 0, the HE STA can enter a doze stateuntil the HE DL MU PPDU ends. (ii) A case that the HE STA receives HE ULMU PPDU (UL FLAG=1) is explained. If BSS color information of a PPDU ismatched with color information of a BSS associated with the HE STA and avalue of a BSS color disabled field of a most recently received HEoperation element corresponds to 0, the HE STA can enter a doze stateuntil the HE UL MU PPDU ends. (iii) A case that the HE STA receives HESU PPDU is explained. If BSS color information of a PPDU is matched withcolor information of a BSS associated with the HE STA, a UL/DL indicatorindicates UL, and a value of a BSS color disabled field of a mostrecently received HE operation element corresponds to 0, the HE STA canenter a doze state until the HE SU PPDU ends.

Having entered the doze state, the STA manages a NAV timer of the STAwhile the STA is in the doze state and may be able to determine that amedium is busy.

Having entered the doze state, if the first frame ends, the STA switchesto an awake state to attempt to access a medium.

In the following, a method of transmitting the abovementioned BSS colordisabled is explained.

To this end, the first embodiment proposes that the BSS color disabledis transmitted to an STA using a broadcast scheme.

FIG. 8 is a diagram illustrating a scheme of informing an STA of BSScolor disabled via a beacon according to one embodiment of the presentinvention.

As shown in FIG. 8, an AP can inform an STA of whether intra-PPDU powersaving is enabled or disabled via a beacon. It is able to inform STAs ofwhether BSS color based intra-PPDU power saving of the STAs is abled ordisabled by adding a new element (e.g., the BSS color disabled) to abeacon frame or adding a new field to a legacy element. When the STAsassociated with the AP receives the beacon frame, if the beacon frameindicates that the BSS color based intra-PPDU power saving is disabled,the STAs do not perform an intra-PPDU power saving operation until theBSS color based intra-PPDU power saving is activated.

A second embodiment proposes that the BSS color disabled is transmittedto an STA based on a request of the STA.

FIG. 9 is a diagram illustrating a scheme of informing an STA of BSScolor disabled via a response message in response to a request of an STAaccording to one embodiment of the present invention.

As shown in FIG. 9, when an AP informs an STA of an activated IP modevia a beacon and the STA performs an IP operation, the STA can make arequest for a status (abled or disabled) of an intra-BSS PPDU powersaving operation to the AP.

Having received a status request of the intra-BSS PPDU power savingoperation from the STA, the AP can transmit a response frame to the STAin a manner of including status information of the intra-BSS PPDU powersaving operation in the response frame. For example, if power savingSTAs fails to obtain intra-PPDU status information via a broadcastmethod, the STAs can obtain the status information (information onwhether intra-PPDU PS is abled or disabled) from the AP using the methodproposed in the second embodiment.

The status request information can be forwarded to the AP in a manner ofbeing piggyback to a different frame or can be delivered to the AP in aform of a request frame.

A third embodiment proposes that BSS color disabled is transmitted to anSTA irrespective of a request of the STA.

FIG. 10 is a diagram illustrating a scheme of informing an STA of BSScolor disabled irrespective of a request of an STA according to oneembodiment of the present invention.

If a status of an intra-BSS PPDU power saving operation is changed(e.g., abled <-> disabled), an AP can transmit a frame to STAs bypiggybacking status information of the intra-BSS PPDU power savingoperation on the frame. For example, the AP may inform the STAs of thestatus information of the intra-BSS PPDU power saving operation byincluding the status information in a HE variant HT control field. Inparticular, the status information can be transmitted in a manner ofbeing included in a ROMI (receiver operation mode indication) HT controlfield of the HE variant HT control field.

The abovementioned schemes can be used in a manner of being combined.For example, in the example shown in FIG. 7, the HE operation elementshown in FIG. 6 can be received in a manner of being included in thefirst frame. Or, the HE operation element can be transmitted in a mannerof being included in a beacon frame/response frame.

The activation/inactivation information transmitted by the AP can betransmitted in a form of a HE control field, an A-MPDU, or a singleMPDU.

Setting of BSS Color Disabled and TXOP Duration Field

As mentioned in the foregoing description, if BSS color is collided witha neighbor BSS, since an STA is able to apply intra-PPDU PS to a PPDUtransmitted by the neighbor BSS, the STA may lose a PPDU transmitted byan AP associated with the STA. One embodiment of the present inventionproposes a method of solving the problem.

If a BSS color collision occurs, as mentioned in the foregoingdescription, the AP informs STAs of the collision (BSS collisionindication) via a beacon frame. Having obtained information on the BSScolor collision, the STAs may not perform an operation related to BSScolor (e.g., intra-PPDU PS, NAV setting).

According to a different embodiment of the present invention, if a BSScolor collision occurs, the AP may select a new BSS color and may bethen able to inform STAs of the new BSS color via a beacon. In thiscase, in order to make all STAs accessing a BSS receive the new BSScolor, the AP informs the STAs of information on the new BSS color andthe BSS color collision for a sufficiently long time.

According to a preferred embodiment of the present invention, when HESTAs belonging to a corresponding BSS receive a beacon from an AP andtransmit HE PPDU to the AP, a TXOP duration field of HE-SIG A is set toa specific value differentiated from a general duration value during acorresponding period, i.e., until a new BSS color is applied. Forexample, the TXOP duration field of the HE-SIG A can be set to all is(127). Of course, it is able to use a specific value corresponding tothe aforementioned situation as well. In the following, an example ofconfiguring the TXOP duration field of the HE-SIG A by all is (127) isexplained. By doing so, it may be able to prevent an error of adifferent STA due to a wrong NAV (network allocation vector) setting.

NAV Update Operation of STA

In a WLAN system, medium access of an STA is performed based on physicalsensing and logical sensing and the logical sensing is performed via NAVcontrol of the STA.

For example, if an STA receives a valid frame not transmitted to theSTA, the STA updates a NAV of the STA based on a duration field value ofthe frame and determines that a medium is busy while a corresponding NAVtimer operates.

Specifically, if an STA receives one or more valid frames from a PSDU,the STA can update a NAV of the STA via a duration field of the PSDU.Yet, if an RA field of the PSDU is identical to a MAC address of theSTA, the STA does not update the NAV of the STA.

However, as mentioned in the foregoing description, if an AP recognizesa BSS color collision and transmits a frame of which a duration value isset to all is to an STA, it is preferable that the STA does not update aNAV of the STA via the frame.

Meanwhile, flax system considers a method for an STA to separatelymanage a NAV for a BSS of the STA and a NAV for a different BSS. In thefollowing, the method is explained.

A HE STA can manage heterogeneous NAVs including an intra-BSS NAVcorresponding to a NAV for the internal of a BSS and an inter-BSS NAVcorresponding to a NAV for the external of a BSS. Among the intra-BSSNAV and the inter-BSS NAV, the inter-BSS NAV can be referred to as aregular NAV. Of course, such a term as the regular NAV can be changed.

When an STA manages the two NAVs, if the STA receives a PSDU of anintra-BSS frame, the STA can update the intra-BSS NAV according toduration field information of the received PSDU. If the STA receives aPSDU of an inter-BSS frame, the STA can update the regular NAV accordingto duration field information of the received PSDU.

In the foregoing description, an example of updating a NAV based on aduration field of a received PSDU has been explained. In this case, itis able to identically update the intra-BSS NAV or the regular NAV usinga TXOP duration of HE SIG-A of a received HE PPDU as well.

If an RA field of a received frame indicates an STA itself, the STA doesnot update a corresponding NAV. If the RA field of the received framedoes not indicate the STA itself, it may be able to update acorresponding NAV based on a duration field of a PSDU or TXOP durationfield information of HE SIG-A according to whether the received framecorresponds to an inter-BSS frame or an intra-BSS frame.

In particular, if a specific STA supports two NAVs, one or more NAVs areconsidered among the two NAVs, and one or more NAV counters are not 0, avirtual CS may determine that a medium is busy.

When the two NAVs are managed, if such a frame as a CTS frame and an ACKframe incapable of being identified as an inter-BSS frame or anintra-BSS frame is received, it is regulated as an STA updates aninter-BSS NAV (regular NAV). In particular, as mentioned in theforegoing description, if BSS color is disabled, similar to a caseincapable of distinguishing an inter-BSS frame from an intra-BSS frame,the present invention proposes that an STA updates the inter-BSS NAV(regular NAV).

Yet, as mentioned in the foregoing description, if an AP configuresduration value by a specific value (e.g., all 1s) differentiated from anormal duration value, it may be preferable not to update the inter-BSSNAV as well.

FIG. 11 is a diagram for explaining a scheme of controlling a NAVsetting according to one embodiment of the present invention.

As shown in FIG. 11, if an AP detects a collision of BSS color, the APcan transmit a beacon of which a BSS color disabled field is set to 1 toan STA. subsequently, in order to prevent wrong NAV update of the STA,the AP sets a value of a TXOP duration field of a PPDU to all 1s.

Having received a frame to which the TXOP duration field is set, the STAdoes not update a NAV of the STA.

Subsequently, if BSS color change is completed, the AP sets a BSS colordisabled field to 0 and can transmit the BSS color disabled field to theSTA.

In particular, when a TXOP duration field of HE-SIG A is set to all 1s(i.e., 127), although BSS color corresponds to intra-BSS color, a HE STAperforms payload decoding (PSDU) to obtain MAC duration withoutperforming intra-PPDU PS. In particular, if the TXOP duration field isset to all is (127), the HE STA does not enter a doze state and does notupdate a NAV.

Meanwhile, when BSS color is disabled, a case that a HE STA receives anintra-PPDU of which TXOP duration is set to a normal value (i.e., avalue rather than all 1s) is explained.

FIG. 12 is a diagram for explaining a scheme of updating a NAV when TXOPduration has a normal value according to one embodiment of the presentinvention.

As shown in FIG. 12, assume a case that an AP configures BSS colordisabled by 1 in the present embodiment. Since the BSS color isdisabled, it is unable to determine whether a PPDU corresponds to anintra-PPDU or an inter-PPDU. Hence, it is preferable to update a basicNAV instead of an intra-BSS NAV using a value set to a TXOP durationfield considering the PPDU as an unidentified PPDU.

In summary, a condition for determining a received frame as an intra-BSSframe is shown in the following.

TABLE 3 A frame received by the STA is an intra-BSS frame if one of thefollowing conditions is true: The RXVECTOR parameter BSS_COLOR in thereceived PPDU carrying the frame is the same as the BSS color announcedby the AP to which the STA is associated and the most recently receivedHE Operation element from the AP to which it is associated contained avalue of 0 in the BSS Color Disabled subfield

And, a condition for updating an intra-BSS NAV of an STA to which theabovementioned content is reflected can be summarized as follows.

TABLE 4 A STA shall update the intra-BSS NAV with the durationinformation indicated by the RXVECTOR parameter TXOP_DURATION if andonly if all the following conditions are met: The RXVECTOR parameterTXOP_DURATION is not set to all 1 s The PPDU that carried information ofthe RXVECTOR parameter is identified as intra-BSS according to the ruledescribed in 27.2.1 (Intra-BSS and inter-BSS frame detection) and themost recently received HE Operation element from the AP to which it isassociated contained a value of 0 in the BSS Color Disabled subfield TheSTA does not receive a frame with the duration information indicated bya Duration field in the PSDU of the PPDU carrying the RXVECTOR parameterTXOP_DURATION The duration information indicated by the RXVECTORparameter TXOP_DURATION is greater than the STA's current intra-BSS NAVThe PPDU that carried information of the RXVECTOR parameter is not an HEtrigger-based PPDU triggered by the STA

FIG. 13 is a diagram for explaining a scheme of updating a NAV when TXOPduration is set to all is according to one embodiment of the presentinvention.

In particular, when a BSS color disabled subfield, which is included ina HE operation element most recently received from an AP associated withan STA, is set to 1, although RXVECTOR parameter BSS_COLOR is identicalto BSS_COLOR of the AP associated with the STA, the STA does notconsider it as an intra-BSS frame. Hence, the STA does not update anintra-BSS NAV. A corresponding frame is considered as an unidentifiedframe and an RXVECTOR TXOP_DURATION field of a received PPDU is updatedto a basic NAV. Of course, if a TXOP_duration field of a received frameis set to all 1s, it is preferable for the STA not to update the basicNAV as well.

Duration Set to all 1s and EIFS Operation

According to the abovementioned method, when OBSS STAs receive acorresponding PPDU, since a TXOP field is set to all 1s, the STAs do notupdate a NAV using the TXOP duration field for the PPDU. Hence, there isa problem that the PPDU is not protected.

In order to solve the problem, if it fails to decode MAC data payloadfor a received PPDU, one embodiment of the present invention proposes toinvoke an EIFS operation.

Specifically, if an intra-PPDU (if BSS color of a received PPDU isidentical to BSS color of an AP associated with a HE STA, the receivedPPDU is regarded as a BSS color based intra-PPDU) is received, the HESTA of which BSS color is disabled does not update both an intra-BSS NAVand a basic (regular) NAV using a TXOP duration field. In particular,the HE STA ignores a value of the TXOP duration field. If the HE STAfails to decode MAC data payload for the received PPDU, the HE STAinvokes an EIFS operation. In particular, although a valid TXOP_durationparameter is included in RXVECTOR of the received PPDU (i.e., if TXOPduration field value is not set to all 1s, it is regarded as valid), ifBSS color is disabled (BSS color disabled subfield is set to 1), EIFScan be invoked.

If a valid TXOP_duration parameter is included in RXVECTOR of a receivedPPDU and a BSS color disabled subfield, which is included in a HEoperation element most recently received from an associated AP, is setto 0, EIFS is not invoked.

It may be able to summarize as Table 5 in the following.

TABLE 5 A DCF of HE STAs shall use EIFS before transmission, when itdetermines that the medium is idle following reception of a frame forwhich the PHY-RXEND.indication primitive contained an error or a framefor which the FCS value was not correct and the most recently receivedHE Operation element from the AP to which it is associated contained avalue of 0 in the BSS Color Disabled subfield. EIFS shall not be invokedif a valid TXOP_DURATION parameter is present in the RXVECTOR of areceived HE PPDU and the most recently received HE Operation elementfrom the AP to which it is associated contained a value of 0 in the BSSColor Disabled subfield

Apparatus Configuration

FIG. 14 is a block diagram for an exemplary configuration of an AP (or abase station) and an STA (or a UE) according to one embodiment of thepresent invention.

An AP 100 can include a processor 110, a memory 120, and a transceiver130. An STA 150 can include a processor 160, a memory 170, and atransceiver 180.

The transceiver 130/180 can transmit/receive a radio signal andimplement a physical layer according to IEEE 802 system. The processor110/160 is connected with the transceiver 130/180 and can implement aphysical layer and/or a MAC layer according to IEEE 802 system. Theprocessor 110/160 is configured to perform an operation according to oneor a combination of two or more embodiments of the present invention. Amodule for implementing operations of the AP and the STA according tothe various embodiments of the present invention is stored in the memory120/170 and the module can be executed by the processor 110/160. Thememory 120/170 can be connected with the processor 110/160 via awell-known media in a manner of being included in the processor 110/160or being installed in the outside of the processor 110/160.

Explanation on the AP 100 and explanation on the STA 150 can berespectively applied to a base station and a user equipment in adifferent wireless communication system (e.g., LTE/LTE-A system).

The configurations of the AP and the STA as described above may beimplemented such that the above-described embodiments can beindependently applied or two or more thereof can be simultaneouslyapplied, and description of redundant parts is omitted for clarity.

FIG. 15 is a diagram for an exemplary configuration of a processor of anAP or an STA according to one embodiment of the present invention.

A processor of an AP or an STA may have a structure of a plurality oflayers. FIG. 15 mainly shows a MAC sublayer 3810 and a physical layer3820 on a DLL (data link layer) among a plurality of the layers. Asshown in FIG. 15, the PHY 3820 can include a PLCP (physical layerconvergence procedure) entity 3821 and a PMD (physical medium dependent)entity 3822. Both the MAC sublayer 3810 and the PHY 3820 includemanagement entities conceptually referred to as an MLME (MAC sublayermanagement entity) 3811. The entities 3811/3821 provide a layermanagement service interface in which a layer management function isoperating.

In order to provide a precise MAC operation, an SME (station managemententity) 3830 exists in each STA. The SME 3830 corresponds to alayer-independent entity capable of exiting in a separate managementplane or capable of being seen as a separate entity (off to the side).Although precise functions of the SME 3830 are not explained in detailin the present specification, the entity 3830 is in charge of collectinglay-dependent status from various layer management entities andsimilarly configuring values of layer-specific parameters. In general,the SME 3830 performs the aforementioned functions on behalf of ageneral system management entity and may be able to implement a standardmanagement protocol.

The entities shown in FIG. 15 interact with each other using variousschemes. FIG. 15 shows several examples of exchanging GET/SETprimitives. XX-GET.request is used to request a value of a given MIBattribute (management information-based attribute information). Ifstatus corresponds to “success”, XX-GET.confirm primitive returns anappropriate MIB attribute information value. Otherwise, theXX-GET.confirm primitive is used to return an error indication to astatus field. XX-SET.request primitive is used to request that anindicated MIB attribute is configured by a given value. If the MIBattribute corresponds to a specific operation, it indicates that the MIBattribute requests to perform the specific operation. If statuscorresponds to “success”, XX-SET.confirm primitive confirms that an MIBattribute is configured by a requested value. Otherwise, theXX-SET.confirm primitive is used to return an error condition to astatus field. If the MIB attribute corresponds to a specific operation,it confirms that the specific operation has been performed.

As shown in FIG. 15, the MLME 3811 and the SME 3830 can exchange variousMLME_GET/SET primitives with each other via an MLME_SAP 3850. And,various PLCM_GET/SET primitives can be exchanged between the PLME 3821and the SME 3830 via a PLME_SAP 3860 and can be exchanged between theMLME 3811 and the PLME 3821 via a MLME-PLME_SAP 3870.

The embodiments of the present invention may be implemented throughvarious means, for example, hardware, firmware, software, or acombination thereof.

When implemented as hardware, a method according to embodiments of thepresent invention may be embodied as one or more application specificintegrated circuits (ASICs), one or more digital signal processors(DSPs), one or more digital signal processing devices (DSPDs), one ormore programmable logic devices (PLDs), one or more field programmablegate arrays (FPGAs), a processor, a controller, a microcontroller, amicroprocessor, etc.

When implemented as firmware or software, a method according toembodiments of the present invention may be embodied as a module, aprocedure, or a function that performs the functions or operationsdescribed above. Software code may be stored in a memory unit andexecuted by a processor. The memory unit is located at the interior orexterior of the processor and may transmit and receive data to and fromthe processor via various known means.

Preferred embodiments of the present invention have been described indetail above to allow those skilled in the art to implement and practicethe present invention. Although the preferred embodiments of the presentinvention have been described above, those skilled in the art willappreciate that various modifications and variations can be made in thepresent invention without departing from the spirit or scope of theinvention. For example, those skilled in the art may use a combinationof elements set forth in the above-described embodiments. Thus, thepresent invention is not intended to be limited to the embodimentsdescribed herein, but is intended to accord with the widest scopecorresponding to the principles and novel features disclosed herein. Thepresent invention may be carried out in other specific ways than thoseset forth herein without departing from the spirit and essentialcharacteristics of the present invention. Therefore, the aboveembodiments should be construed in all aspects as illustrative and notrestrictive. The scope of the invention should be determined by theappended claims and their legal equivalents, and all changes comingwithin the meaning and equivalency range of the appended claims areintended to be embraced therein. The present invention is not intendedto be limited to the embodiments described herein, but is intended toaccord with the widest scope consistent with the principles and novelfeatures disclosed herein. In addition, claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by subsequent amendment after the application is filed.

And, both an apparatus invention and a method invention are explained inthe present specification and the explanation on the both of theinventions can be complementally applied, if necessary.

INDUSTRIAL APPLICABILITY

The present invention can be applied to various wireless systemsincluding IEEE 802.11 system.

What is claimed is:
 1. A method for a non-AP (Access Point) STA(Station) maintaining a first NAV (Network Allocation Vector) for anintra-BSS (Basic Service Set) frame and a second NAV for an inter-BSSframe in a WLAN (Wireless Local Area Network) system, the methodcomprising: receiving BSS (Basic Service Set) color disabled informationset to a first value from an AP; receiving, from the AP, a framecomprising: a TXOP_DURATION field set to a specific value other thannormal duration values in response that the BSS color disabledinformation is set to the first value, and BSS color information; andupdating the first NAV or the second NAV based on classification of thereceived frame as the intra-BSS frame or the inter-BSS frame, whereinthe STA updates the second NAV in response that the received framecannot be classified as the intra-BSS frame or the inter-BSS frame, andwherein the BSS color information of the received frame is not used forclassification of the received frame in response that the BSS colordisabled information is set to the first value.
 2. The method of claim1, wherein, in response that the TXOP_DURATION field is set to thespecific value, the STA does not update the first NAV.
 3. The method ofclaim 1, wherein the received frame cannot be classified as theintra-BSS frame or the inter-BSS frame when the BSS color disabledinformation is set to the first value.
 4. The method of claim 1,wherein, in response that the TXOP_DURATION field is set to the specificvalue, the STA operates based on an EIFS (extended inter-frame space).5. The method of claim 1, wherein the specific value of theTXOP_DURATION field corresponds to a value that all bits are set to 1.6. A non-AP (Access Point) STA (Station) operating in a WLAN (WirelessLocal Area Network) system, the non-AP STA comprising: a memorymaintaining a first NAV (Network Allocation Vector) for an intra-BSS(Basic Service Set) frame and a second NAV for an inter-BSS frame; atransceiver configured for receiving BSS (Basic Service Set) colordisabled information and a frame from an AP, wherein the frame comprisesa TXOP_DURATION field and BSS color information, and wherein aTXOP_DURATION field of the frame is set to a specific value other thannormal duration values in response that the BSS color disabledinformation is set to a first value; a processor connected to the memoryto update the first NAV or the second NAV of the memory, and connectedto the transceiver to process the received frame, wherein the processorupdates the first NAV or the second NAV based on classification of thereceived frame as the intra-BSS frame or the inter-BSS frame, whereinthe processor updates the second NAV in response that the received framecannot be classified as the intra-BSS frame or the inter-BSS frame,wherein the BSS color information of the received frame is not used forclassification of the received frame in response that the BSS colordisabled information is set to the first value.
 7. The non-AP STA ofclaim 6, wherein, in response that the TXOP_DURATION field is set to thespecific value, the processor does not update the first NAV.
 8. Thenon-AP STA of claim 6, wherein the received frame cannot be classifiedas the intra-BSS frame or the inter-BSS frame when the BSS colordisabled information is set to the first value.
 9. The non-AP STA ofclaim 6, wherein, in response that the TXOP_DURATION field is set to thespecific value, the processor operates based on an EIFS (extendedinter-frame space).
 10. The non-AP STA of claim 6, wherein the specificvalue of the TXOP_DURATION field corresponds to a value that all bitsare set to
 1. 11. A method for an AP (Access Point) for controlling anon-AP STA (Station) maintaining a first NAV (Network Allocation Vector)for an intra-BSS (Basic Service Set) frame and a second NAV for aninter-BSS frame in a WLAN (Wireless Local Area Network) system, themethod comprising: transmitting BSS (Basic Service Set) color disabledinformation set to a first value to the non-AP STA; transmitting, to thenon-AP STA, a frame comprising: a TXOP_DURATION field set to a specificvalue other than normal duration values in response that the BSS colordisabled information is set to the first value, and BSS colorinformation; and wherein the first NAV or the second NAV of the non-APSTA is updated based on classification of the frame as the intra-BSSframe or the inter-BSS frame, wherein the STA updates the second NAV inresponse that the received frame cannot be classified as the intra-BSSframe or the inter-BSS frame, and wherein the BSS color disabledinformation set to the first value informs the non-AP STA that the BSScolor information of the frame cannot be used for classification of theframe.
 12. An AP (Access Point) for controlling a non-AP STA (Station)maintaining a first NAV (Network Allocation Vector) for an intra-BSS(Basic Service Set) frame and a second NAV for an inter-BSS frame in aWLAN (Wireless Local Area Network) system, the AP comprising: atransceiver transmitting BSS (Basic Service Set) color disabledinformation and a frame to the non-AP STA; and a processor connected tothe transceiver, wherein the processor configured to: set the BSS colordisabled information to a first value; include, in the frame: aTXOP_DURATION field set to a specific value other than normal durationvalues in response that the BSS color disabled information is set to thefirst value, and BSS color information; and wherein the first NAV or thesecond NAV of the non-AP STA is updated based on classification of theframe as the intra-BSS frame or the inter-BSS frame, wherein the STAupdates the second NAV in response that the received frame cannot beclassified as the intra-BSS frame or the inter-BSS frame, and whereinthe BSS color disabled information set to the first value informs thenon-AP STA that the BSS color information of the frame cannot be usedfor classification of the frame.